This invention relates to a flexible composite sheet suitable for use as a topsheet in a disposable body fluid absorbent sanitary article such as a disposable diaper, a sanitary napkin or the like.
Japanese Patent Application Publication No. 1999-217453A describes a flexible composite sheet comprising a flexible plastic sheet layer and a fibrous layer bonded to a lower surface of the plastic sheet layer. In this composite sheet, the plastic sheet layer is provided with a plurality of opening arrays each having a plurality of openings arranged intermittently in one direction. A plane region of plastic sheet is defined between each pair of the adjacent opening arrays and a plurality of tooth-like portions extend upward from the upper surface of the plane region along edges of the peripheries defining the respective openings, the edges extending in the one direction, so that the tooth-like portions may undulate in the one direction in the form of an irregular wave.
With the composite sheet of prior art, a plurality of the tooth-like portions are flexibly deformed and give the article wearer a velvet-like soft touch as the surface of the composite sheet comes in contact with a wearer""s skin. However, most of the tooth-like portions are arranged to form the irregular waves in the same direction as the direction in which the opening arrays extend. This means that these tooth-like portions are easily collapsed orthogonally to the opening arrays and thereby give a wearer a soft touch but collapsed with a difficulty in the direction in which the opening arrays extend. Consequently, a flexibility in the latter direction is inferior to a flexibility in the former direction. Furthermore, even if such differential flexibility depending on the direction raises no serious problem for use of such composite sheet as the topsheet of the sanitary article, an anisotropy of the composite sheet with respect to its flexibility should undesirably restrict practical use of the composite sheet.
It is an object of this invention to provide a conventional composite sheet in which anisotropy in the flexibility of the sheet surface may be eliminated.
According to this invention, there is provided a composite sheet comprising a sheet-like fibrous assembly having upper and lower surfaces and a film of thermoplastic synthetic resin being intermittently arranged on and bonded to the upper surface of the sheet-like fibrous assembly so that the upper surface is exposed in a plurality of regions.
The composite sheet further comprises the fibrous assembly being formed with fibers having a fineness of 0.5xcx9c20 dtex and a basis weight of 5xcx9c60 g/m2 and the film being formed by a plurality of narrow strips, each having a thickness of 1xcx9c50 xcexcm, intermittently arranged so as to be spaced one from another by a distance of 30xcx9c1000 xcexcm in a first direction and in a second direction intersecting the first direction of the fibrous assembly wherein each of the narrow strips is defined by sides extending in the first and second directions, respectively, along which the narrow strip is formed with a plurality of tooth-like portions rising in a direction from the lower surface toward the upper surface and have proximal ends lying along the sides and distal ends so that the tooth-like portions are tapered from the proximal ends toward the distal ends.
Also, according to this invention, there is provided a process for making a flexible composite sheet by subjecting a composite web comprising a continuous fibrous web having upper and lower surfaces and a continuous film of thermoplastic synthetic resin bonded to the upper surface to the steps of:
a. continuously feeding the composite web in one direction;
b. reciprocating a first group of nozzles in a direction transversely of the one direction, the first group having a plurality of nozzles linearly arranged transversely of the one direction, wherein columnar fluid streams are ejected from the nozzles against the film of the composite web so that the film may be broken in accordance with loci of the nozzles being reciprocated; and
c. reciprocating a second group of nozzles in a direction transversely of the one direction, the second group having a plurality of nozzles linearly arranged transversely of the one direction, wherein columnar fluid streams are ejected from the nozzles against the lower surface of the fibrous web so that broken regions of the film is widened and lengthened and portions of the film remaining along the broken regions are oriented so as to rise in a direction from the lower surface toward the upper surface of the fibrous web.